Most people in the US are enrolled in prescription drug insurance programs with tiered benefits that require higher copayments for brand-name prescriptions than generic versions. In this study, the mean copayment for the index statin prescription was $38 higher for brand-name drug recipients, and the finding of higher adherence to generic statins is therefore unsurprising. This study is however the first to assess clinical effects of such differences in adherence.
The authors acknowledge a number of limitations to their study, including the possibility of bias due to confounding, lack of information on the decision to initiate a generic versus a brand-name statin, the limitation to 3 statins for which generic versions were available in the US at the time (lovastatin, pravastatin, or simvastatin), and use of the intention-to-treat approach (possibly leading to exposure misclassification if switching occurred).
The study included US Medicare beneficiaries aged 65 years or older, and the results may not be generalizable to other populations with different incomes or drug benefit structures (including the NHS).